Player: V10.010.010
A very minor bug. Scroll to the right of the level, then scroll back. Look on the right side of the minimap. A white line stays on the right (seen in GIF below).
(http://i.imgur.com/fuTJeeF.gif)
This only happens on some levels. Unruly 9 "Buzzing Around" and Outrageous 12 "Plan Bee" of Lemmings Plus V are examples that have this problem.
I've noticed this a few times but haven't bothered to do anything about it, given that other fixes with the minimap (eg. better handling of vertical scrolling) are needed anyway. I'll probably address it once I deal with that.
For the record, whether or not this happens depends on the width of the level, though I'm not sure exactly what values will or won't trigger it.
Might be a while until the minimap stuff gets properly fixed, so I implemented a fix to this bug for the next update.